{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T14:19:34Z","timestamp":1784557174112,"version":"3.55.0"},"reference-count":48,"publisher":"Bioscientifica","issue":"1","content-domain":{"domain":["joe.bioscientifica.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2016,10]]},"abstract":"<jats:p>\n                    The 5\u03b1-reductase enzymes play an important role during male sexual differentiation, and in pregnant females, especially equine species where maintenance relies on 5\u03b1-reduced progesterone, 5\u03b1-dihydroprogesterone (DHP). Epididymis expresses 5\u03b1-reductases but was not studied elaborately in horses. Epididymis from younger and older postpubertal stallions was divided into caput, corpus and cauda and examined for 5\u03b1-reductase activity and expression of type 1 and 2 isoforms by quantitative real-time polymerase chain reaction (qPCR). Metabolism of progesterone and testosterone to DHP and dihydrotestosterone (DHT), respectively, by epididymal microsomal protein was examined by thin-layer chromatography and verified by liquid chromatography tandem mass spectrometry (LC-MS\/MS). Relative inhibitory potencies of finasteride and dutasteride toward equine 5\u03b1-reductase activity were investigated. Pregnenolone was investigated as an additional potential substrate for 5\u03b1-reductase, suggested previously from\n                    <jats:italic>in vivo<\/jats:italic>\n                    studies in mares but never directly examined. No regional gradient of 5\u03b1-reductase expression was observed by either enzyme activity or transcript analysis. Results of PCR experiments suggested that type 1 isoform predominates in equine epididymis. Primers for the type 2 isoform were unable to amplify product from any samples examined. Progesterone and testosterone were readily reduced to DHP and DHT, and activity was effectively inhibited by both inhibitors. Using epididymis as an enzyme source, no experimental evidence was obtained supporting the notion that pregnenolone could be directly metabolized by equine 5\u03b1-reductases as has been suggested by previous investigators speculating on alternative metabolic pathways leading to DHP synthesis in placenta during equine pregnancies.\n                  <\/jats:p>","DOI":"10.1530\/joe-16-0175","type":"journal-article","created":{"date-parts":[[2016,7,27]],"date-time":"2016-07-27T22:08:47Z","timestamp":1469657327000},"page":"23-33","update-policy":"https:\/\/doi.org\/10.1530\/crossmarkpolicy-5","source":"Crossref","is-referenced-by-count":15,"title":["Equine 5\u03b1-reductase activity and expression in epididymis"],"prefix":"10.1530","volume":"231","author":[{"given":"C J","family":"Corbin","sequence":"first","affiliation":[{"name":"1Department of Population Health and ReproductionSchool of Veterinary Medicine, University of California, Davis, California, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"E L","family":"Legacki","sequence":"additional","affiliation":[{"name":"1Department of Population Health and ReproductionSchool of Veterinary Medicine, University of California, Davis, California, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"B A","family":"Ball","sequence":"additional","affiliation":[{"name":"2Department of Veterinary ScienceGluck Equine Research Center, University of Kentucky, Lexington, Kentucky, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"K E","family":"Scoggin","sequence":"additional","affiliation":[{"name":"2Department of Veterinary ScienceGluck Equine Research Center, University of Kentucky, Lexington, Kentucky, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"S D","family":"Stanley","sequence":"additional","affiliation":[{"name":"3Department of Molecular BiosciencesSchool of Veterinary Medicine, University of California, 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